docs(storage): clarify example READMEs and when to use each

Update storage example docs so FATFS getting_started and wear_levelling
are clearly distinct, refresh the storage index paths, and add
"When to use this example" sections across storage examples.

examples/storage/fatfs/getting_started/README.md

@@ -1,32 +1,49 @@
 | Supported Targets | ESP32 | ESP32-C2 | ESP32-C3 | ESP32-C5 | ESP32-C6 | ESP32-C61 | ESP32-H2 | ESP32-H21 | ESP32-H4 | ESP32-P4 | ESP32-S2 | ESP32-S3 | ESP32-S31 |
 | ----------------- | ----- | -------- | -------- | -------- | -------- | --------- | -------- | --------- | -------- | -------- | -------- | -------- | --------- |
 
-# FATFS minimal example
+# FATFS getting started (minimal) example
 
 (See the README.md file in the upper level 'examples' directory for more information about examples.)
 
-This example demonstrates the minimal setup required to store persistent data on SPI Flash using the FAT filesystem.
-Beware that the minimal required size of the flash is 4 MB.
+## Purpose
+
+Minimal FAT filesystem example for beginners: mount a FAT volume on internal SPI flash, write one file, read it back, then unmount.
+
+Wear levelling is enabled by the mount API used here (`esp_vfs_fat_spiflash_mount_rw_wl`), which is required for safe read-write FAT on SPI flash.
+
+## When to use this example
+
+- You want the shortest path to store files with FATFS on internal SPI flash.
+- You are learning the basic mount / write / read / unmount flow.
+
+## What this example demonstrates
+
+- Mount FAT on the `storage` partition with `esp_vfs_fat_spiflash_mount_rw_wl`
+- Create and write a file with `fopen` / `fprintf`
+- Read the file back with `fopen` / `fgets`
+- Unmount with `esp_vfs_fat_spiflash_unmount_rw_wl`
+
+Source: [main/fatfs_getting_started_main.c](./main/fatfs_getting_started_main.c)
+
+## Requirements
+
+- Internal SPI flash large enough for the example partition table (typically at least 4 MB modules)
+- Partition label: `storage` (see [partitions_example.csv](./partitions_example.csv))
 
 ## How to use example
 
 ### Build and flash
 
-To run the example, type the following command:
-
-```CMake
-# CMake
+```
 idf.py -p PORT flash monitor
 ```
 
-(To exit the serial monitor, type ``Ctrl-]``.)
+(Replace `PORT` with the serial port name. Exit the serial monitor with ``Ctrl-]``.)
 
 See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.
 
 ## Example output
 
-Here is the example's console output:
-
 ```
 ...
 I (321) example: Mounting FAT filesystem
@@ -39,6 +56,3 @@ I (741) example: Unmounting FAT filesystem
 I (851) example: Done
 ...
 ```
-
-The logic of the example is contained in a [single source file](./main/fatfs_getting_started_main.c),
-and it should be relatively simple to match points in its execution with the log outputs above.